Silencer



NOV. 23, L' L. HAAS 2,100,030

SILENGER Filed June 7, 1934 2 SheetsSheet l Nov. 23, 1937. Y L' L- HAAS 2,100,030

SILENCHR Filed June 7, 1934 2 Sheets-Sheet 2 Patented Nov. 23, 1937 PATENT OFFICE SILENCE!! Lucien L. Haas, Buffalo, N. Y., assignor to Buffalo Pressed Steel Company, Inc., Buffalo, N. Y.

Application June 7, 1934, Serial No. 729,451

19 Claims.

This invention relates to improvements in silencers or muiliers, particularly of the type employed for the silencing of the exhaust from internal combustion engines.

The objects of this invention are to provide an improved muilier of the type in which the gases, instead of flowing straight through the mufiler from one end thereof to the other, have their direction of flow changed within the muiiier; also to provide a .nuiiler of this type within which a pair of gas conducting and sound attenuating units are arranged in overlapped relation to each other Within the muiller, and in which a shell surrounding the units is used to conduct the gases from one of the sound attenuating units to the other.

Other objects of the invention are to provide a muiiler of this type with an outer annular sound attenuating chamber surrounding the sound attenuating units; also to construct a muffler of this type in such a manner that the inner sound attenuating units are acoustically insulated from the outer shell of the muiller for the purpose of eliminating certain noises caused by direct contact of the sound attenuating units with the outer shell of the muiiier; also to provide a muiiler of this kind with a space that may be divided by a baille or baiiies into a number of sound attenuating chambers, so that by mere change in position of a baille, or by increasing or decreasing the number of bafes, the dimensions of the sound attenuating chambers and their actions on certain sound waves or frequencies can be varied; also to improve the construction of mulers of this type in other respects hereinafter specified and claimed.

In the accompanying drawings:

Fig. 1 is a longitudinal central sectional view of one type of muiiier embodying this invention;

Figs. 2, 3 and 4 are transverse sectional elevations thereof, on lines 2 2, 3 3, 4 4, respectively, of Fig. 1;

Figs. 5, 6 and l are longitudinal central sectional elevations of muillers of somewhat modied constructions;

Fig. 8 is a transverse sectional elevation on line 8 8, Fig. 7.

Referring to Fig. 1, I0 represents the outer shell or casing of the muiiler which has heads Il and I2 secured to the ends thereof, the head il being provided with an inlet opening and the head I2 with an outlet opening. Within the muiiler are arranged a number of sound attenuating and gas conducting units preferably extending parallel to each other and in tangential and overlapping relation to each other, although it is not essential that the units be in tangential or over-lapping relation to each other. The muiilers shown in the drawings represent relatively simple embodiments of my invention and in these muiilers only two sound attenuating units are used, although more of such units may be employed, if desired, or only one sound attenuating unit may be employed, and the other sound attenuating unit may be replaced by a conduit for the exhaust gas. One of these units communicates with the aperture in the head II, and the other unit connects with the aperture in the head I 2 at the discharge end of the muiiier.

These sound attenuating units may be of any suitable or desired construction, and in the particular muiiler ,illustrated in Fig. 1, the sound attenuating unit connecting with the inlet head II includes an inner conduit or tube I4 provided with perforations throughout the greater portion of the length thereof and a substantially imperforate tube I5 surrounding the conduit Il and spaced therefrom by means of one or more annular baiiles I6. The openings in the conduit I4 are of relatively small size, and preferably the inner conduit I4 has portions thereof pressed outwardly at the perforations in this shell to form louvcrs il. When such louvcrs are used, the gases and sound waves discharged through the apertures in the inner conduit Il are deilected tangentially to produce a spinning or whirling movement of the gases and sound waves in the sound attenuating spaces or chambers between the inner conduit I4 and the shell I5. Preferably, the louvcrs in different chambers extend alternately in opposite directions as shown in the drawings.

The other sound attenuating member may be similar to the one which has already been described, and as shown also includes an inner perforated conduit 20 and a substantially imperforate tube 2| surrounding the same and spaced therefrom by means of one or more 'cailles 22 to form sound attenuating chambers about the conduit. This conduit, as shown, connects with a short tube 24 extending through the head I2 and the usual tail pipe (not shown) leading from the muiller may be connected to this tube. The iirst sound attenuating unit connects with an inlet tube or passage 25 extending through the head I i and to which the exhaust pipe from the engine may be connected.

The first sound atienuating unit connecting with the inlet head II terminates at a. distance 1mm the other head I2, and the other sound attenuating unit communicating with the aperture in the head I2, terminates at a distance from the inlet head il. Consequently, exhaust gases discharged from the rst unit have their direction of iiow reversed and pass backwardly on the exterior of the two sound attenuating units into the receiving end of the second unit and after passing through this second unit, are discharged into the tail pipe. 'Ihe two units, as clearly shown in Fig. 3, are preferably arranged in contact with each other and may, if desired, be Welded to-` gether, so that the two units produce a relatively strong and rigid construction, and so that rattling is prevented, but these units may be arranged within the muiiier in spaced relation to each other, and may be secured against rattling in other ways. As shown in Fig. 3, spaces 26 and 21 are provided outside of the units through which the gases 110W from the rear to the front end of the muiiier, which spaces together are of much greater cross-sectional area than the cross-sectional area of the conduits i4 or 20. Consequently, the gases are expanded after discharge from the conduit |4, which assists in silencing noise and reducing back pressure of the muiiier. It has been found that in muillers in which sound'attenuating units of this type are employed and arranged in contact with the outer shell of the muilier, a certain pinging sound is produced when pulsations or impulse waves from the engine pass into the muiiier, which sounds can be heard within the body of the vehicle. I have found that this objection can be overcome by providing within the outer-shell il), a shell 28 spaced at a distance from the outer shell, and I also utilize the space between these two shells as resonator chambers, by means of which certain low frequency sound waves can be attenuated, which are not eliminated in the sound attenuating units which have already been described.

The space between the shells 28 and i0 may be employed in any suitable or desired manner to attenuate sound waves, and in the particular construction shown in Fig. 1, I divide this space into two sound attenuating or resonating chambers 30 and 3| by means of a baille 32. I also provide perforations in the opposite end portions of the shell 28, such perforations 33 near the discharge end of the muilier communicating with one end of the resonating chamber 3i, and corresponding apertures 34 near the inlet head H communicating with one end of the chamber 30. These apertures may be in the` nature of spinner slots as used on the inner conduits Mi and 2@ by forming louvers on the shell 23 at the apertures therein. This arrangement of the apertures in the shell '28 will cause gases and sound waves to be deilected tangentially into the end portions of the resonating chambers and by admitting these sound waves at one end of each chamber, the imperforate portion of each chamber will act as a resonating chamber.l By varying the lengths of these resonating chambers by changing the position of the bale 32, this portion of the muiler can be tuned to eliminate different sound waves. It is well known that diierent engines produce different noises in the exhaust and a muiiier which is entirely satisfactory on engines. of one design will be noisy when used on an engine of other design. .By means of the constructionv described, thebaiile 32. can lie-shiftedv to eliminate certain low frequency sound waves, and the higher frequency sound waves can be eliminated by varying the dimensionsof the two sound attenuating units which have been described, or by other means.

The construction shown in Fig. -5 is Similar to that described in connection with Fig. 1, except that the first sound attenuating unit is shorter than that shown in Fig. 1, and the space between the outer shell 4I of the muier and the adjacent shell 42 is divided into three silencing or resonator chambers 43, 44 and 45 by ,means of bailies 46 and 41. As in the construction shown in Fig. 1, thechamber receives gases and sound waves through a series of apertures 48 in the shell 42 near the end thereof, and the chamber 43 receives gases and sound waves through a series of apertures 49. A third set of apertures 50 is provided in the shell 42 through which gases and sound waves may enter one end of the resonator chamber 44.

Fig. 6 illustrates another muler of modified form embodying my invention. In the 'case of this muiiier, in addition to the two end heads, an intermediate head is employed. The outer shell 56 of this muiler extends from the inlet head 51 to the outlet head 58, and the second shell 59 spaced adjacent thereto extends from the inlet head 51 to the intermediate head 55. The shell 59 is provided with apertures 6i through which gases and sound waves may pass after passing through-the rst sound attenuating unit i 62, and another series of apertures 53 are provided at the other end of the shell 59, both of these apertures communicating withresonance chambers formed between the shells 55 and 59 and separated by a bailie 60. i

A sound attenuating chamber e5 of different form is employedin this muiiier between the heads 55 and 58 and the gas and sound conducting conduit of the second sound attenuating unit extends through the chamber (i5, and is provided with openings 51 in the portion thereof yextending into this chamber. This arrangement produces a whirling action of the gases when the conduit 66 is provided with louvers El as shown in the drawings and by arranging the conduit eccentrically within the chamber $5, a sound attenuating effect is produced which has been found very eiective for certain types of noises, since sound waves, whirling about the conduit 66 in the eccentric chamber surrounding this conduit are more effectively attenuated than when whirling in a concentric annular chamber.

It will be noted too that in the rst sound attenuating unit 52, one of the chambers 59 is of greater length than the length of the perforated portion of the inner conduit extending through the same, and a similar arrangement is provided in 'connection with the second sound attenuating unit in which a similar chamber l@ is provided. The portions of these chambers about the imperforate parts of the inner conduit form resonators which act to destroy certain sounds.

Figs. 7 and 8 show still another modification of my invention. In the muiler shown in these iigures, an intermediate headl5 is provided which with the discharge head 'i6 forms an expansion chamber 'il for the gases after passing through the sound attenuating units of the mumer. means of this construction, the discharge outlet forming a part of the rear head 'i6 may be formed in any convenient location, and need not be in alinement with the second sound attenuating unit of the muler. In the construction shown, this outlet 'i8 to which the tail pipe may bev connected is formed centrally on the discharge head 16.

' In this munier only a single resonating chamber 88 is formed between the outer shell 8| and the adjacent shell 82. It will be noted also that the shell 82 is arranged eccentrically with reference to the outer shell 8l, see particularly Fig. 8, and the shell 82 is provided with apertures 83 communicating with the resonating chamber 88. In this construction, such apertures are only used at one end of the shell 82, but if desired, a baille may be arranged in the chamber 80, in which case, apertures could also be provided near the other end of the shell 82.

By discharging gases and sound waves substantially tangentially into an annular chamber, the walls of which are eccentric with reference to the conduit from which the gases are discharged, as in the case of the chamber 88 in Figs. 7 and 8, and in the chamber 65 in Fig. 6, the sound waves are subjected in their passage around the eccentric chamber to travel between alternately converging and diverging walls of the chamber. This'has a distorting or modifying effect on the sound waves which is even more eiective in reducing sounds than when such waves pass around an annular chamber.

At the inlet end of this muier, a short inlet tube 85 is employed which terminates at a distance from the adjacent end of the inner conduit 86 of the first sound attenuating unit, thus form ing an expansion chamber 81 into which the gases pass upon first entering the muiiier. An expansion chamber of this type may, of course, be used in connection with any of the other constructions which have been illustrated, and such chambers are eiective in decreasing certain sounds and in decreasing the degree of impulse Waves entering the muiiier.

In all of the muiiiers described, certain pinging sounds or shell noises, which are produced in muiilers in which the outer shells are secured to or contact directly with some of the sound attenuating units, are entirely eliminated by the provision of chambers between the sound attenuating units and the outer shells of the mufers,

and these chambers by means of the constructions illustrated also serve as resonator cham-` bers, and thus serve the dual purpose of elimihating shell noise as well as different fundamental sounds and their harmonics. 'I'he muiliers in the form shown in the drawings are of strong and rigid construction, in that the outer shells or tubes of the two sound attenuating units of each muflier may be secured together, for example, by welding, and these tubes in turn may be Welded to the inner shell of the outer resonance spaces of the mufiiers, so that the several tubular parts reinforce eachv other.

In the operation of muiiiers of the kind shown in the drawings, the exhaust gases and sound waves from the engine first pass into the rst sound attenuating unit which includes a number of chambers communicating with the inner conduit through the perforations therein. Each of these chambers eliminates certain sounds, mostly of high frequency type, and also the tops or crests of the impulse waves entering the muiiler are eliminated in these chambers. The exhaust gases then pass out of the rst sound attenuating unit into the space near the discharge end of the muiiler where their path of movement is reversed, and if at this point apertures are provided at the inner shell of the outer resonance chamber, other sound waves of lower frequency are destroyed or modified. The gases then pass toward the inlet end of the muliler in the relatively large spaces surrounding the sound attenuating units and within the inner. shell of the outer resonance chambers, and at the front or inlet end of the muilier, additional apertures may be provided in this shell, communicating with an outer resonance chamber tuned to attenuate still other sound waves. 'I'he action upon 'the sound waves and gases in passing through the second sound attenuating unit is much the same as in the iirst one and by the time the gases and sound waves reach the tail pipe, assuming that the muffler is proportioned and properly tuned for a particular type of engine, with which it is used, will be substantially ree from noises. Because of the relatively largel area. of the return passages connecting the two sound attenuating units, there will be comparatively little back pressure produced in muiiiers of this type, and the expansion of the gases in this part of the muiiier also has the effect of reducing noise and impulse waves.

By means of the construction described, the manufacture of muiiiers of the reverse flow type is greatly simplied for the reason that only two gas conducting conduits are arranged within the muiiier, and a shell surrounding these conduits constitutes a return passage for the gases, thus eliminating the usual additional transverse baiiies which are needed when a third or return conduit is used.

I clailn as my invention:

1. A muilier including an imperforate outer shell, heads to which the opposite ends of said shell are connected and provided with openings for inlet and discharge of exhaust gases, a second shell arranged within said outer shell and spaced therefrom to form with said outer shell a resonator chamber, a pair of conduits arranged side by side within said second shell, one of said conduits receiving gases at one end thereof from the inlet opening and the other conduit discharging gases from the other end thereof through the discharge opening in the other head, each of said conduits terminating at their other ends at distances from said heads, at least one of said conduits being perforated throughout the greater portion of the length thereof, means arranged about the perforated portion of said conduit to form therewith a sound attenuating chamber, said second shell forming a return duct in which gases flow in a direction opposite to that in said conduits, said second shell having apertures to permit gases and sound waves to enter said resonator chamber.

2. A muflier including a shell and heads connected therewith and spaced apart, one of said heads being provided with an inlet opening for exhaust gases and the other head being provided with an outlet therefor, a pair of sound attenuating and gas conducting units arranged side by side in said shell, one of said units receiving exhaust gases from said inlet opening in one head and terminating within said muiller at a distance from the other head, and the other unit communicating with the discharge opening in the other head and terminating within said muiiler at a distance from said first head, each of said units being of approximately half of the inside diameter of said shell and secured thereto, the portions of the shell surrounding said units providing for a return flow of gases from one of said units to the other, and an outer shell surrounding and spaced from said rst mentioned shell to form therewith a resonance chamber in communication with the interior of said muiier, said first mentioned shell having an opening located adjacent to an end of the muflier lll chamber.

3. A muiiier including a pair of sound` attenuating units, each including an inner perforate openended conduit and a tubular member arranged about -said inner conduit, said units being arranged in overlapping relation to each other, the overlapping portions of said units contacting with each other, a tubular member arranged about both units and contacting with the same, one of said units receiving gases at one end thereof and discharging the same into the interior of said tubular member, and theother u nit receiving gases from the interior of said tubular member and discharging the same from the muiiier, said sound attenuating units dividing the interior of said tubular member into two passages in which gases may flow from one unit to the other in a direction opposite to that in which gases ow in said units. 4. A muiiier including three sound attenuating members, each comprising an inner perforate conduit and a shell surrounding said conduit to form a sound attenuating chamberv between the conduit and shell, two of said sound attenuating members being of not more than half of the diameter of the interior of the other sound attenuating member and being arranged in overlapping relation to each other within said other sound attenuating member, one of the inner sound attenuating members receiving gas at one endrand discharging the same into the interior of said third sound attenuating member, and the other inner sound attenuating member receiving gases from the interior of said third sound attenuating member and conducting the same to the discharge of said 'muiiien 5. A muier including three tubular sound attenuating and gas conducting units, each corpprising an inner perforate conduit and a shell arranged about said conduit, and forming a sound attenuating chamber between said shell and conduit, the conduit of one of said units having its inner diameter at least equal to the combined outer diameters of 'the shells of the other two units, and having its shell form the outer shell of the muiiier, said other two units being arranged in overlapping relation to each other within the larger unit, heads closing the ends of said larger unit, the conduits and shells of said inner units terminating near the opposite ends of said larger unit and at distances from said heads, whereby said larger unit conducts gases about said inner units from one inner unit to the other in a direction opposite to the direction of ow of gases in said inner units.

6. A mufiier including a shell, heads connected therewith and spaced apart and being provided with openings for the inlet and discharge of exhaust gases to and from said muiiier, a pair of gas conducting conduits arranged in overlapping relation to each other within said shell, at least one of said conduits having a perforate portion, sound attenuating means arranged about said perforate portion of said conduit, one conduit receiving gases from the inlet opening and the other conduit discharginggas through the outlet opening of the muiiier, said shell forming a return passage connecting the other ends of said conduits,

and means associated with said shell to form chambers communicating with the interior of said muiiler for attenuating sounds discharged into said muiiier by said rst mentioned unit.

l '7. A muiiler including a shell, heads connected therewith and spaced apart and provided with Aopenings for the inlet and discharge of gases, a

conduit arranged within said shell and receiving gases through an opening in one of said heads and terminating at a distance from the otherv head, a second conduit arranged to discharge gases through the opening in the other head and terminating at a distance from said rst head, said conduits being arranged in overlapping relation to each other within said shell, whereby said shell constitutes a return duct for 'conducting gases from one conduit to the other, sound attenuating chambers associated with at least one of said conduits, andan outer shell surrounding said first mentioned shell to form a chamber communicating with the interior of said muiiierv for attenuating sounds discharged into said muiiler by said iirst mentioned unit, said chamber receiving sound waves from said return duct.

,8. A muilier including a pair of outer shells spaced apart one within the other toform between them an annular sound attenuating chamber, a pair of conduits for exhaust gases arranged within said shells and in overlapping relation to veach other and through which gases flow in one direction,one of said conduits discharging gases into the space conned by the inner of said outer shells and the other conduit receiving gases from. said space to produce a reverse flow of gases in said space about said conduits, the inner of said outer shells having apertures for admitting sound waves to the chamber formed between said outer shells to attenuate sound waves.

9. A muier including a pair of outer shells arranged one within the other in spaced relation to each other to form between them a resonator chamber, means for producing a reverse iiow of gases within said muler, including a plurality of gas conducting and sound attenuating units having conduits for exhaust gases, one of said conduits discharging gases near one end o the inner of said shells and the other of said conduits receiving said gases near the other end of said inner shell, the inner of said shells constituting a y conduit for the reversely owing gases, and being apertured for admitting sound Waves from the gases confined by the inner of said shells into said resonator chamber.

10. A muiiierprovided with means for producing a reverse ow of gases therein and including a pair of outer shells spaced apart one within the other and forming between them a resonating chamber, the inner of said shells having an opening through which sound waves from said exhaust gasesmay be admitted to said resonating chamber, the inner of said shells also constituting a conduit for the gases when flowing in the reverse direction.

11. A muffler including an imperforate outer shell, heads to which the opposite ends of said shell are connected and provided with openings for inlet and discharge of exhaust gases, a second shell arranged within said outer shell and spaced therefrom to form with said outer shell a lresonator chamber, a pair of gas conducting and sound attenuating units arranged in overlapping relation to each other within said second shell and each includingvan inner perforate conduit and a shell surrounding said conduit to form therewith a sound attenuating chamber, the shell of one unit being arranged in contact with the A shell of the other unit, anboth of the shells of said units contacting with the second shell, the conduit of one of said units receiving gases at one end thereof from said inlet'opening and discharging gases in said muilier adjacent to the head thereof having the outlet opening, the conduit of the other sound attenuating unit being connected at one end with said discharge opening and terminating within said muffler adjacent to the head having the inlet opening, said second shell forming a return duct for gases discharged into said muier by said irst unit and conducting said gases to the inner end of said second unit, said second shell having apertures to permit gases and sound waves to enter into said resonator chamber.

12. A muffler including a pair of conduits extending into the same, one conduit extending into the muiller from one end thereof, and the other conduit extending into the muiiier from the other end thereof, said conduits being arranged in overlapping relation to each other, a shell surrounding both of said conduits and having portions thereof spaced from said conduits to form a return passage from one conduit to the other, means associated with at least one of said conduits to form a sound attenuating chamber, and means associated with said shell for forming a sound attenuating chamber about said return passage.

13. A muilier of the reverse flow type in which the exhaust gases iiow rst toward the discharge end thereof, then toward the inlet end thereof and then again toward the discharge end, said muiiier including conduits for the gases and a shell surrounding said conduits and to which said conduits are secured at their sides, said conduits having open ends terminating within said shell and said shell serving to conduct gases from the open end of one conduit to the open end of the other conduit, and an outer shell surrounding said first mentioned shell and spaced therefrom to form a chamber between said yshells to deaden shell noises, and an opening in said first mentioned shell through which gases and sound waves may pass into and out of said chamber, said opening being adjacent to an open end of one of said conduits.

14. A muffler including three tubular sound attenuating and gas conducting units, the internal diameter of one of which is at least equal to the combined external diameter of the other two units, each of said units including a perforate conduit and means forming a sound attenuating chamber about the conduit, said other two units being arranged in overlapping relation to each other within the larger unit, heads closing the ends of the larger unit, one of said heads having an inlet for gas connecting with one of the inner units and the other head having a discharge opening for gas communicating with the other inner unit, said inner units terminating within said larger unit at distances from said heads and said larger unit conducting gases from one inner unit to the other in a direction opposite to that in which gases ow in said inner units.

15. A muiiier including an outer shell and end heads, one of which has an inlet opening through which gases may enter the muiiler and the other of which has a discharge opening for gases, an inlet conduit connected with said inlet opening and discharging gases into the interior of said muiiler, a second conduit connecting with said discharge Aopening and having perforate portions, a second shell about said perforate portions forming therewith an acoustical expansion chamber, the portion of said muier between said outer shell and said inlet conduit and said second shell being substantially unobstructed to form a return ow passage from one conduit to the other and forming an expansion chamber for gases between pressure impulses transmitted to the muiiler.

16. A muiiier including an outer shell and end heads, one of which has an inlet opening through which gases may enter the muiiier and the other of which has a discharge opening for gases, an inlet conduit connected with said inlet opening and discharging gases into the interior of said muiiier, a second conduit connecting with said discharge opening and having perforate portions, a second shell about said perforate portions forming therewith an acoustical expansion chamber, the portion of said muilier between said outer shell and said inlet conduit and said second shell being substantially unobstructed to form a return ilow passage from one conduit to the other and forming an expansion chamber for gases between pressure impulses transmitted to the muiiier, said first mentioned conduit having perforations and means within said muiiler for preventing gases discharged through said perfora- -tions of the iirst mentioned conduit from impinging directly on said outer shell.

17. A muiier of the return ilow type including an outer shell and end heads, one of which is provided with an inlet opening and the other of which has-a discharge opening, an inlet conduit connected with said inlet opening and a discharge conduit connected with said discharge opening, said conduits extending into the interior of said muflier into overlapping relation to each other, said discharge conduit being perforate, an intermediate shell arranged about the perforations of said discharge conduit to form therewith an acoustical expansion chamber, the space within said outer shell and about said inlet conduit and intermediate shell being substantially unobstructed and forming a return flow passage of materially greater cross sectional area than that of said conduits and forming an expansion chamber for reducing pressure pulsations discharged into said muiiier through said inlet conduit.

18. A muffler of the return iiow type including an outer shell and end heads, one of which is provided with an inlet opening and the other of Which has a discharge opening, an inlet conduit connected with said inlet opening and a discharge conduit connected with said discharge opening, said conduits extending into the interior of said muiiler into overlapping relation to each other, said discharge conduit being perforate, an intermediate shell arranged about the perforations of said discharge conduit to form therewith an acoustical expansion chamber, said muiiler being provided with a return iiow passage leading from said inlet to said discharge conduit which is of materially greater cross sectional area than that of said conduits and which forms an expansion chamber for reducing pressure pulsations discharged into said muiiier through said inlet conduit.

19. A muiller of the return flow type including an outer housing having inlet and outlet conduits arranged in overlapping relation therein, said outlet conduit being perforate, a shell about said outlet conduit and forming therewith an acoustical expansion chamber, said housing forming a return duct for gases from said inlet conduit to said outlet conduit and being of materially greater cross sectional area than that of either of said conduits.

LUCIEN L. HAAS. 

